Beautiful little jewel of a lens, a Steinheil of Munchen Cassar lens originally intended for enlarging/process work, it will of course work as a taking lens as well. Coated, very clean optics, barrel is very good also and aperture is clean and smooth.
I mounted this on a 4x5 camera to test coverage, it covers the format at 5ft, may have soft corners at infinity, so in a pinch you can use this as a 4x5 enlarging lens but it's probably intended for 6x6 to 6x9 work. Does not come with retaining ring.